Dental caries formation involves a very complex series of interactions between a mixed microbial population, the host tissue and ingested substrates. Plaque pH telemetry is used to measure the acidogenic potential of various dietary components. This is not a direct measure of cariogenicity since the disease itself is not being measured. It is necessary to be able to relate acidogenicity measurements to dental caries cariogenicity. This grant proposes to measure de- and re-mineralization at the very earliest stages of dental decay simultaneously with acidogenicity measurements. This will be accomplished by placing thin tooth sections into an intra-oral appliance also containing indwelling pH electrodes. Thus the acidogenicity of a normal or specified diet may be measured along with the resultant hard tissue changes. The development of this unique model system will enable the correlation of plaque pH responses with de- or re-mineralization of tooth sections. Specifically, the establishment of a reasonable time frame for demineralization of coronal and/or root surfaces will be investigated. Differences between interproximal versus buccal sites will be tested. The effect of plaque pH on both sound and caries-like tissue will also be examined. Having established a model system for the formation of caries-like lesions using an intra-oral applicance, coupled with changes in plaque pH, a unique opportunity exists to evaluate various preventive agents and their mechanisms of action. The experiments will use polarized light microscopy, microradiography and scanning electron microscopy to evaluate any hard tissue changes such as demineralization or remineralization of existing caries-like lesions. pH telemetry will be used to follow a patients plaque pH response on representative days of the test periods. These results will be used to calculate an approximate acidogenic challenge which will then be correlated to the changes observed in the hard tissue histology. Thus a more thorough understanding of the mechanism of dental caries will be gained from the interaction of preventive agents with the host and/or microbial population, which will lead to the application of preventive agents in a more efficient manner.